Measurement of Casing Step Effects on Turbopump Inducer Cavitation Performance

Abstract

In a liquid rocket engine, a turbopump is used to supply low-pressure, low-temperature fuel and liquid oxidizer to the combustor. This circumstance causes cavitation in the impeller of the turbopump. To solve the performance degradation and vibration problem of the impeller due to the cavitation, an inducer is installed in front of the impeller. In this study, effects of casing step on cavitation performance has been investigated. Upstream and downstream of inducer, static pressures have been measured to determine head coefficient and cavitation number, and cavitation phenomenon has been visualized using high speed camera. In the range of cavitation number above 0.07, there is no difference in head coefficient of the casing with step and the casing without step. However, in the range of cavitation number below 0.07, head coefficient of the casing without step is higher than head coefficient of the casing with step. According to the visualization results in the range of cavitation number below 0.07, backflow cavitation was not suppressed in casing without step. This backflow cavitation blocks main flow path, and varies inlet flow structure. This makes suppression of tip leakage cavitation growth, which affects head coefficient.